Calcium & aquatic organisms

Fish: Calcium affects how easily water, salts, and harmful microbes pass through skin and gills, and
is linked to kidney health.

Crustaceans (e.g. crabs and lobsters): Absorb large amounts of calcium after moulting to harden new shells, for protection against predators and disease.

Bivalves (e.g. mussels and oysters): Continuously take in calcium to build and grow their shells.

Seaweed: Because they lack roots, seaweeds absorb calcium from the water for healthy growth.